The present invention relates to the unloading of bulk bags used as containers for dry or moist particulate materials. The present invention more particularly relates to the unloading of bulk bag containers fabricated from cloth like material, such as woven polyester material, which is usually sewn in a cubical configuration.
Bulk bags 2 made of heavy cloth material have been known in the art for sometime. It has also been known to provide the bag with heavy corner straps 4 which support the bag 2 when it is hung in a tower like support frame 6. The opposite end of the bag 2 typically has a central outlet spout 5 which is aligned with a discharge unit 10, for example a conveyer, hopper or the like, into which the material in the bag 2 is intended to be discharged.
To discharge the bag 2, the bag 2 is hung in the support frame 6 and the spout 5 engaged with the discharge unit 10. The spout 5 is opened and the particulate material flows via gravity through the spout 5. It is a characteristic of some particulate materials contained in a bag to resist or stop flowing out of the spout 5 when the material remaining in the bag 2 reaches the material's angle of repose or bridges over the spout 5. Since the bottom of the bag 2, extending from the spout 5 to the walls, is typically not at angle greater than the material's angle of repose, not all of the material will be discharged through the spout 5 by gravity. The material remaining in the bag 2 after the discharge by gravity often forms a cone shape inside the container. The inner face of this cone shape, formed by the granular material, extends from the spout 5 in the bottom of the bag 2 upward at an angle to the wall of the bag 2. The angle of repose at which this cone shape occurs and discharge by gravity ends depends on the physical characteristics of the bulk material involved.
To promote flow and reduce the likelihood of stacking of material along the walls, it is known in the art to use rotatable plate assemblies 12 adjacent the bottom of the bag 2. The rotatable plates rotate from a substantially horizontal position to an inclined position to push the bottom corners of the bag 2 inward to promote flow towards the central spout 5. While the rotatable plate assemblies 12 have proven successful in helping promote flow, some materials having a high angle of repose and resistance to flowing freely still tend to stack along the walls of the bag 2.
Accordingly, there is a need for an apparatus which promotes flow of the material stacking along the walls of the bag.